gnupg1orig: add -fcommon workaround

Workaround build failure on -fno-common toolchains like upstream
gcc-10. Otherwise build fails as:

    ld: ../util/libutil.a(estream-printf.o):/build/gnupg-1.4.23/util/../include/memory.h💯 multiple definition of
        `memory_debug_mode'; gpgsplit.o:/build/gnupg-1.4.23/tools/../include/memory.h💯 first defined here

pkgs/tools/security/gnupg/1.nix

@@ -11,6 +11,12 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ readline bzip2 ];
 
+  # Workaround build failure on -fno-common toolchains like upstream
+  # gcc-10. Otherwise build fails as:
+  #   ld: ../util/libutil.a(estream-printf.o):/build/gnupg-1.4.23/util/../include/memory.h:100: multiple definition of
+  #     `memory_debug_mode'; gpgsplit.o:/build/gnupg-1.4.23/tools/../include/memory.h:100: first defined here
+  NIX_CFLAGS_COMPILE = "-fcommon";
+
   doCheck = true;
 
   meta = with lib; {